In the related art, a technology is known which checks a driver condition or provides a driver with awareness by detecting a predetermined driving operation. For example, Patent Literature 1 discloses an awareness degree assessment device that enhances an assessment accuracy of driver's degree of awareness by changing the assessment standard which assesses driver's degree of awareness based on whether a preceding vehicle is present. Further, when the preceding vehicle is continuously present for a fixed time within a range of a fixed distance from a host vehicle, a normal steering amount which is steering angle in a normal consciousness state, is calculated by using a preceding vehicle data. Thereafter, a technology is also known which assesses whether a driver consciousness has degraded by using the normal steering amount that has been calculated when the preceding vehicle is present within a fixed distance.